Chapter 8
CLASSIFICATION OF DATA
The principal value of vital statistics data is realized through the
presentation of rates, which are computed by relating the vital events
of a class to the population of a similarly defined class. Vital
statistics and population statistics must therefore be classified
according to similarly defined systems and tabulated in comparable
groups. Even when the variables common to both, such as geographic area,
age, sex, and race, have been similarly classified and tabulated,
differences between the enumeration method of obtaining population data
and the registration method of obtaining vital statistics data may
result in significant discrepancies.
The general rules used in the classification of geographic and personal
items for deaths and fetal deaths for 1991 are set forth in two NCHS
instruction manuals (2,3). A discussion of the classification of certain
important items is presented below.
Classification by occurrence and residence
Tabulations for the United States and specified geographic areas in
this volume are classified by place of residence unless stated as by
place of occurrence. Before 1970, resident mortality statistics for the
United States, included all deaths occurring in the United States with
deaths of "nonresidents of the United States" assigned to place of
death. "Deaths of nonresidents of the United States" refers to deaths
that occur in the United States of nonresident aliens; nationals
residing abroad; and residents of Puerto Rico, the Virgin Islands, Guam,
and other territories of the United States. Beginning with 1970, deaths
of nonresidents of the United States are not included in tables by place
of residence.
Tables by place of occurrence, on the other hand, include deaths of
both residents and nonresidents of the United States. Consequently, for
each year beginning with 1970, the total number of deaths in the United
States by place of occurrence was somewhat greater than the total by
place of residence. For 1991 this difference amounted to 3,542 deaths.
Mortality statistics by place of occurrence are shown in tables 1-11,
1-19, 1-20, 1-30, 1-31, 1-32, 3-1, 3-6, 8-1, and 8-7.
Before 1970, except in 1964 and 1965, deaths of nonresidents of the
United States occurring in the United States were treated as deaths of
residents of the exact places of occurrence, which in most instances
were urban areas. In 1964 and 1965 deaths of nonresidents of the United
States occurring in the United States were allocated as deaths of
residents of the balance of the county in which they occurred.
Residence error--Results of a 1960 study showed the classification
of residence information on the death certificates corresponded
closely to the residence classification of the census records
for the decedents whose records were matched (4).
A comparison of the results of this study of deaths with those for a
previous matched record study of births (5) showed the quality of
residence data had improved considerably between 1950 and 1960. Both
studies found that events in urban areas were overstated by the NCHS
classification in comparison with the U.S. Bureau of the Census
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classification. The magnitude of the difference was substantially less
for deaths in 1960 than it was for births in 1950.
The improvement is attributed to an item added in 1956 to the U.S.
Standard Certificates of Birth and of Death, asking whether residence
was inside or outside city limits. This new item aided in properly
allocating the residence of persons living near cities but outside the
corporate limits.
Geographic classification
The rules followed in the classification of geographic areas for
deaths and fetal deaths are contained in the two instruction manuals
referred to previously (2,3). The geographic codes assigned by the NCHS
during data reduction of source information on birth, death, and
fetal-death records are given in another instruction manual (6).
Beginning with 1982 data, the geographic codes were modified to reflect
results of the 1980 census. For 1970-81, codes are based on results of
the 1970 census.
Metropolitan statistical areas--The Metropolitan statistical areas
(MSA's) and Primary metropolitan statistical areas (PMSA's) used in this
volume are those established by the U.S. Office of Management and Budget
as of April 1, 1990, and used by the U.S. Bureau of the Census (7),
except in the New England States.
Outside the New England States, an MSA has either a city with a
population of at least 50,000 or a Bureau of the Census urbanized area
of at least 50,000 and a total MSA population of at least 100,000. A
PMSA consists of a large urbanized county or cluster of counties that
demonstrate very strong internal economic and social links and has a
population over 1 million. When PMSA's are defined, the larger area of
which they are component parts is designated a Consolidated Metropolitan
Statistical Area (CMSA) (8).
In the New England States, the U.S. Office of Management and Budget uses
towns and cities rather than counties as geographic components of MSA's
and PMSA's. However, NCHS cannot use this classification for these
States because its data are not coded to identify all towns. Instead,
NCHS uses New England County Metropolitan Areas (NECMA's). Made up of
county units, these areas are established by the U.S. Office of
Management and Budget (9).
Metropolitan and nonmetropolitan counties--Independent cities and
counties included in MSA's and PMSA's or in NECMA's are included in data
for metropolitan counties; all other counties are classified as
nonmetropolitan.
Population-size groups--In 1991, vital statistics data for cities
and certain other urban places were classified according to the
population enumerated in the 1980 Census of Population. Data are
available for individual cities and other urban places of 10,000 or more
population. Data for the remaining areas not separately identified are
shown in the tables under the heading "balance of area" or "balance of
county." For the years 1970-81, classification of areas was determined
by the population enumerated in the 1970 Census of Population. Beginning
with 1982 data, some urban places identified in previous reports were
deleted and others were added because of changes occurring in the
enumerated population between 1970 and 1980.
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Urban places other than incorporated cities for which vital
statistics data are shown in this volume include the following:
. Each town in the New England States, New York, and Wisconsin and each
township in Michigan, New Jersey, and Pennsylvania that had no
incorporated municipality as a subdivision and had either 25,000
inhabitants or more, or a population of 10,000 to 25,000 and a density of
1,000 persons or more per square mile.
. Each county in States other than those indicated above that had no
incorporated municipality within its boundary and had a density of 1,000
persons or more per square mile. (Arlington County, Virginia, is the only
county classified as urban under this rule.)
. Each place in Hawaii with a population of 10,000 or more. (There are no
incorporated cities in the State.)
Before 1964, places were classified as "urban" or "rural." The
technical appendixes for earlier years discuss the previous
classification system.
State or country of birth
Mortality statistics by State or country of birth (table 1-36)
became available beginning with 1979. State or country of birth of a
decedent is assigned to 1 of the 50 States, the District of Columbia; or
to Puerto Rico, the Virgin Islands, or Guam--if specified on the death
certificate. The place of birth is also tabulated for Canada, Cuba,
Mexico, and for the Remainder of the World. Deaths for which information
on State or country of birth was unknown, not stated, or not
classifiable accounted for a small proportion of all deaths in 1991,
about 0.6 percent.
Early mortality reports published by the U.S. Bureau of the Census
contained tables showing nativity of parents as well as nativity of
decedent. Publication of these tables was discontinued in 1933.
Mortality data showing nativity of decedent were again published in
annual reports for 1939-41 and for 1950.
Age
The age recorded on the death record is the age at last birthday.
With respect to the computation of death rates, the age classification
used by the U.S. Bureau of the Census is based also on the age of the
person in completed years. For computation of age-specific and
age-adjusted death rates, deaths with age not stated are excluded. For
life table computation, deaths with age not stated are distributed
proportionately.
Race
For vital statistics in the United States for 1991, deaths are
classified by race--white, black, American Indian, Chinese, Hawaiian,
Japanese, Filipino, Other Asian and Pacific Islanders, and Other.
Mortality data for Filipino and Other Asian or Pacific Islander were
shown for the first time in 1979.
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The white category includes, in addition to persons reported as
white, those reported as Mexican, Puerto Rican, Cuban, and all other
Caucasians. The American Indian category includes American, Alaskan,
Canadian, Eskimo, and Aleut. If the racial entry on the death
certificate indicates a mixture of Hawaiian and any other race, the
entry is coded to Hawaiian. If the race is given as a mixture of white
and any other race, the entry is coded to the appropriate nonwhite race.
If a mixture of races other than white is given (except Hawaiian), the
entry is coded to the first race listed. This procedure for coding the
first race listed has been used since 1969. Before 1969, if the entry
for race was a mixture of black and any other race except Hawaiian, the
entry was coded to black.
Most of the tables in this volume, however, do not show data for
this detailed classification by race. In all the tables, the divisions
are white, all other (including black), and black separately.
Race not stated--For 1991, the number of death records for which
race was unknown, not stated, or not classifiable was 5,609, or 0.3
percent of the total deaths. Death records with race entry not stated
are assigned to a racial designation as follows: If the preceding record
is coded white, the code assignment is made to white; if the code is
other than white, the assignment is made to black. Before 1964, all
records with race not stated were assigned to white except records of
residents of New Jersey for 1962-64.
New Jersey, 1962-64--New Jersey omitted the race item from its
certificates of live birth, death, and fetal death used in the beginning
of 1962. The item was restored during the latter part of 1962. However,
the certificate revision without the race item was used for most of 1962
as well as 1963. Therefore, figures by race for 1962 and 1963 exclude
New Jersey. For 1964, 6.8 percent of the death records used for
residents of New Jersey did not contain the race item.
Adjustments made in vital statistics to account for the omission of
the race item in New Jersey for part of the certificates filed during
1962-64 are described in the technical appendixes of the Vital
Statistics of the United States for each of those data years.
Quality of race data--A number of studies have been conducted on the
reliability of race reported on the death certificate. These studies compare
race reported on the death certificate with that reported on another data
collection instrument such as the census or a survey. Differences may arise
in the results of the studies because of differences in who provides race
information on the compared records. Race information on the death
certificate is reported by the funeral director as provided by an informant,
often the surviving next of kin, or, in the absence of an informant, on the
basis of observation. In contrast, race on the census or the Current
Population Survey (CPS) is self-reported and, therefore, may be considered
more valid. A high level of agreement between the death certificate and the
census or survey report is essential to ensure unbiased death rates by race.
In one study a sample of approximately 340,000 death certificates was
compared with census records for a 4-month period in 1960 (10). Percent
agreement was 99.8 percent for white decendents, and 98.2 percent for black
decedents; but less for the smaller minority groups (table A). In another
study 29,713 death certificates were compared with responses to the race
questions from a total of 12 CPS's conducted by the U.S. Bureau of the
Census for the years 1979-85. In this study, entitled the National Longi-
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tudinal Mortality Study, agreement for white decendents was 99.2 and for
black 98.2; agreement was less for the smaller race groups. In 1986
the National Mortality Followback Survey, conducted by NCHS, listed a
question about the race of decendents 25 years old and over. The total
sample was 18,733 decendents (12). The rates of agreement were similar to
those observed in the other studies.
Table A. Comparison of percent agreement and ratio of deaths for census or
survey record to deaths by race for matching death certificate:
1960 and 1979-85
_____________________________________________________________________________
Census NLMS1/
_______________________ ___________________
Ratio Ratio
census/ NLMS/
Percent death Percent death
Race agreement certificate agreement certificate
_____________________________________________________________________________
White 99.8 1.00 99.2 1.00
Black 98.2 1.00 98.2 1.00
American Indian 79.2 1.12 73.6 1.22
Asian --- --- 82.4 1.12
Japanese 97.0 1.04 --- ---
Chinese 90.3 1.07 --- ---
Filipino 72.6 1.28 --- ---
_____________________________________________________________________________
1/ NLMS is defined as National Longitudinal Mortality Study.
SOURCES: Hambright TZ. Comparability of marital status, race, nativity,
and country of origin on the death certificate and matching census record:
U.S., May-August 1960. National Center for Health Statistics. Vital Health
Stat 2(34). 1969; Sorlie PD, Rogot E, Johnson NJ. Validity of demographic
characteristics on the death certificate. Epidemiology 3(2):181-4. 1992.
All of these studies show that persons self-reported as American Indian
or Asian on census and survey records (and by informants in the Followback
Survey) were sometimes reported as white on the death certificate. The
net effect of misclassification is an underestimation of deaths and death
rates for the smaller minority races.
Quality of data on Hispanic origin--A recent study (11) examined the
reliability of Hispanic origin reported on 43,520 death certificates with
that reported on a total of 12 CPS's conducted by the U.S. Bureau of the
Census for the years 1979-85. In this study, agreement was 89.7 percent for
any report of Hispanic origin. The ratio of deaths for CPS divided by deaths
for death certificate was 1.07 percent indicating net underreporting of
Hispanic origin on death certificates as compared with self reports on the
surveys. The sample was too small to assess the reliability of specified
Hispanic groups.
Hispanic origin
Mortality statistics for the Hispanic-origin population are based on
information for those States and the District of Columbia that included
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items on the death certificate to identify Hispanic or ethnic origin of
decedents. Data for 1991 were obtained from the District of Columbia and
all States except New Hampshire, and Oklahoma. Hispanic mortality data
were published for the first time in 1984. Generally, the reporting
States used items similar to one of two basic formats recommended by
NCHS. The first format is directed specifically toward the Hispanic
population and appears on the U.S. Standard Certificate of Death
as follows:
Was decedent of Hispanic origin?
(Specify No or Yes-If Yes, specify Cuban, Mexican,
Puerto Rican, etc.) ___ No ___ Yes
Specify:
The second format is a more general ancestry item and appears as
follows:
Ancestry - Mexican, Puerto Rican, Cuban, African,
English, Irish, German, Hmong, etc.,(specify)
For 1991, mortality data in tables 1-37 and 2-24 are based on deaths
to residents of all 48 reporting States and the District of Columbia. In
tables 1-38, 1-43, and 1-44, mortality data for the Hispanic-origin
population are based on deaths to residents of 47 States, New York State
(excluding New York City), and the District of Columbia whose data were
at least 90 percent complete on a place-of-occurrence basis and
considered to be sufficiently comparable to be used for analysis. Data for
New York City are excluded from tables 1-38, 1-43, and 1-44 because of the
large proportion of deaths (in excess of 10 percent) occurring in this
geographic area for which Hispanic origin was not stated or was unknown.
Because New York City accounts for about a third of the deaths to Puerto
Ricans, the resulting mortality data may not be comparable with previous
years. New Hampshire and Oklahoma were excluded because their death
certificates did not have an Hispanic or ancestry item.
In tables 2-25--2-28, the reporting area is based on deaths to
residents of the same 47 States, New York State (excluding New York
City), and the District of Columbia whose mortality data for all ages
and whose live birth data were at least 90 percent complete on a
place-of-occurrence basis and considered to be sufficiently comparable
to be used for analysis.
The 47 States, New York State (excluding New York City), and the
District of Columbia for which general mortality data are shown in this
report accounted for about 91 percent of the Hispanic population in the
United States in 1990. This included about 99 percent of the Mexican
population, 63 percent of the Puerto Rican population, 94 percent of the
Cuban population, and 83 percent of the "Other Hispanic" population
(13). Accordingly, some caution should be exercised in generalizing
mortality patterns from the reporting area to the Hispanic-origin
population (especially Puerto Ricans) of the entire United States. For
qualifications regarding infant mortality of the Hispanic-origin
population, see "Infant deaths."
Connecticut--For deaths occurring in Connecticut in 1991, a number of
deaths were erroneously coded. For Mexicans there should have been 7 deaths,
not 318 deaths; and for Puerto Ricans, there should have been 371 deaths, not
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215 deaths. As a result, the number of deaths for the 47 States, New York
(excluding New York City), and the District of Columbia for Mexicans should
be about 1 percent less and the number for Puerto Ricans should be about 3
percent more than the figures shown.
Marital status
Mortality statistics by marital status (tables 1-34 and 1-35) were
published in 1979 for the first time since 1961. (They were previously
published in the annual volumes for 1949-51 and 1959-61.) Several
reports analyzing mortality by marital status have been published,
including the special study based on 1959-61 data (14). Reference to
earlier reports is given in the appendix of part B of the 1959-61
special study.
Mortality statistics by marital status are tabulated separately for
never married, married, widowed, and divorced. Certificates on which the
marriage is specified as being annulled are classified as never married.
Where marital status is specified as separated or common-law marriage,
it is classified as married. Of the 2,116,483 resident deaths 15 years
of age and over in 1991, 10,103 certificates (0.5 percent) had marital
status not stated.
Educational attainment
Beginning with the 1989 data year, mortality data on educational
attainment are being tabulated from information reported on the death
certificate. As a result of the revisions of the U.S. Standard
Certificate of Death (1), this item was added to the certificates of a
large number of States:
. Decedent's Education (specify only highest grade completed)
. Elementary/Secondary (0-12) College (1-4 or 5+)
Mortality data on educational attainment for 1991 (table 1-45) are
based on deaths to residents of 44 States, New York(excluding New York City),
and the District of Columbia. Data for five States--Georgia, Oklahoma,
Rhode Island, South Dakota, and Washington--are excluded from this table
because their death certificates did not include an educational attainment
item, and data for New York City are excluded because the education item on
its death certificate was considered not comparable to be used for analysis.
In tables 1-46 and 1-47, the data are based on deaths to residents
of 30 States, New York (excluding New York City), and the District of
Columbia whose data were at least 90-percent complete on a place-of-
occurrence basis. The 30 States are Alabama, Arizona, California, Colorado,
Delaware, Florida, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Louisiana,
Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, New
Hampshire, North Dakota, Ohio, Oregon, Pennsysvania, South Carolina, Texas,
Utah, Vermont, Wisconsin, and Wyoming. Data for Alaska, Arkansas,
Connecticut, Kentucky, Maine, Maryland, Mississippi, Nevada, New Jersey, New
Mexico, North Carolina, Tennessee, Virginia, and West Virginia are excluded
because more than 10 percent of their death certificates were classified to
"unknown educational attainment."
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Place of death and status of decedent
Mortality statistics by place of death were published in 1979 for
the first time since 1958 (tables 1-30--1-32). In addition, mortality
data also were available for the first time in 1979 for the status of
decedent when death occurred in a hospital or medical center. The 1991
data were obtained from the following two items appearing on the revised
U.S. Standard Certificate of Death: (1)
. Item 9a. Place of Death (check only one)
Hospital: Inpatient, ER/Outpatient, DOA
Other: Nursing Home, Residence, Other(specify)
. Item 9b. Facility Name (If not institution, give street and number)
Before the 1989 revision of the Standard Certificate of Death,
information on place of death and status of decedent could be determined
if the hospital or institution indicated Inpatient, Outpatient, ER, and DOA,
and if the name of the hospital or institution, which was used to determine
the kind of facility, appeared on the certificate. The change to a checkbox
format in many States for this item may affect the comparability of data
between 1989 and previous years.
Except for Oklahoma, all of the States (including New York City)
and the District of Columbia have item 9 (or its equivalent) on their
certificates. Louisiana's certificate was revised in 1989, but the
computer system was not changed. Therefore, the same detail categories
used in 1988 were used in 1989 and 1990. As a result, not all categories
were available. For all reporting States and the District of Columbia in
the VSCP, NCHS accepts the state definition, classification, or code for
hospitals, medical centers, nursing homes, or other institutions.
Effective with data year 1980, the coding for place of death and
status of decedent was modified. A new coding category was added: "Death
on arrival--hospital, clinic, medical center name not given." Deaths
coded to this category are tabulated in tables 1-30--1-32. Had the 1979
coding categories been used, these deaths would have been tabulated as
"Place unknown."
California--For the first five months of data year 1989, California
coded "residence" to "other" for "Place of Death."
Mortality by month and date of death
Deaths by month have been tabulated regularly and published in the
annual volume for each year beginning with data year 1900. For 1991
deaths by month are shown in tables 1-20, 1-21, 1-24, 1-33, 2-14--2-16,
and 3-7.
Date of death was published for the first time for data year
1972. In addition, unpublished data for selected causes by date of death
for 1962 are available from NCHS.
Numbers of deaths by date of death in this volume are shown in table 1-33
for the total number of deaths and for the numbers of deaths for the
following three causes, for which the greatest interest in date of occurrence
of death has been expressed: Motor vehicle accidents, Suicide, and Homicide
and legal intervention.
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These data show the frequency distribution of deaths for the
selected causes by day of the week. They also make it possible to
identify holidays with peak numbers of deaths from specified causes.
Report of autopsy
Before 1972, the last year for which autopsy data were tabulated was
1958. Beginning in 1972, all registration areas requested information on
the death certificates as to whether an autopsy was performed. For
1991, autopsies were reported on 233,707 death certificates, 10.8
percent of the total (table 1-29).
Information indicating whether autopsy findings were used in
determining the cause of death was tabulated for 1972-73 for all but
nine registration areas and for 1974-77 for all but eight registration
areas. The item "autopsy findings used" was deleted from the 1978 U.S.
Standard Certificate of Death.
For nine of the cause-of-death categories shown in table 1-29,
autopsies were reported as performed for 50 percent or more of all
deaths (Shigellosis and amebiasis; Measles: Pregnancy with abortive outcome;
Other complications of pregnancy, childbirth, and the puerperium;
Symptoms, signs, and ill-defined conditions; Motor vehicle accidents;
Suicide; Homicide and legal intervention; and All other external causes).
Autopsies were reported for only 6.9 percent of the Major cardiovascular
diseases.
Cause of death
Cause-of-death classification--Since 1949, cause-of-death
statistics have been based on the underlying cause of death, which is
defined as "(a) the disease or injury which initiated the train of
events leading directly to death, or (b) the circumstances of the
accident or violence which produced the fatal injury" (15).
For each death, the underlying cause is selected from an array of
conditions reported in the medical certification section on the death
certificate. This section provides a format for entering the cause of
death sequentially. The conditions are translated into medical codes
through use of the classification structure and the selection and
modification rules contained in the applicable revision of the
International Classification of Diseases (ICD), published by the World
Health Organization (WHO). Selection rules provide guidance for
systematically identifying the underlying cause of death. Modification
rules are intended to improve the usefulness of mortality statistics by
giving preference to certain classification categories over others
and/or to consolidate two or more conditions on the certificate into one
classification category.
As a statistical datum, underlying cause of death is a simple,
one-dimensional statistic; it is conceptually easy to understand and a
well-accepted measure of mortality. It identifies the initiating cause
of death and is therefore most useful to public health officials in
developing measures to prevent the onset of the chain of events leading
to death. The rules for selecting the underlying cause of death are
included in ICD as a means of standardizing classification, which
contributes toward comparability and uniformity in mortality medical
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statistics among countries.
Tabulation lists--Beginning with data year 1979, the cause-of-death
statistics published by NCHS have been classified according to the Ninth
Revision of the International Classification of Diseases (15). In
addition to specifying that ICD-9 be used, WHO also recommends how the
data should be tabulated to promote international comparability. The
recommended system for tabulating data in ICD-9 allows countries to
construct their mortality and morbidity tabulation lists from the
rubrics of the WHO Basic Tabulation List (BTL) if the rubrics from the
WHO mortality and morbidity lists, respectively, are included. This
tabulation system for the Ninth Revision is more flexible than that for
the Eighth Revision, in which specific lists were recommended for
tabulating mortality and morbidity data.
The BTL recommended under the Ninth Revision consists of 57
two-digit rubrics that when added equal the "all causes" total.
Identified within each two-digit rubric are up to nine three-digit
rubrics that are numbered from zero to eight and whose total does not
equal the two-digit rubric. The two-digit BTL rubrics 01 through 46 are
used for the tabulation of nonviolent deaths according to ICD categories
001-799. Rubrics relating to chapter 17 (nature-of-injury causes 47
through 56) are not used by NCHS for selecting underlying causes of
death; rather, preference is given to rubrics E47 through E56. The 57th
two-digit rubric VO is the Supplementary Classification of Factors
Influencing Health Status and Contact with Health Services and is not
appropriate for the tabulation of mortality data. The WHO Mortality
List, a subset of the titles contained in the BTL, consists of 50
rubrics that are the minimum necessary for the national display of
mortality data.
Five lists of causes have been developed for tabulation and
publication of mortality data in this volume--the Each-Cause List, List
of 282 Selected Causes of Death, List of 72 Selected Causes of Death,
List of 61 Selected Causes of Infant Death, and List of 34 Selected
Causes of Death. These lists were designed to be as comparable as
possible with the NCHS lists more recently used under the Eighth
Revision. However, complete comparability could not always be achieved.
The Each-Cause List is made up of each three-digit category of the
WHO Detailed List to which deaths may be validly assigned and most
four-digit subcategories. The list is used for tabulation for the entire
United States. The published Each-Cause table does not show the
four-digit subcategories provided for Motor vehicle accidents
(E810-E825); however, these subcategories that identify persons injured
are shown in the accident tables of this report (section 5). Special
fifth-digit subcategories also are used in the accident tables to
identify place of accident when deaths from nontransport accidents are
shown. These are not shown in the Each-Cause table.
The List of 282 Selected Causes of Death is constructed from BTL
rubrics 01-46 and E47-E56. Each of the 56 BTL two-digit titles can be
obtained either directly or by combining titles in the List. The
three-digit level of the BTL is modified more extensively. Where more
detail was desired, categories not shown in the three-digit rubrics were
added to the List of 282 Selected Causes of Death. Where less detail was
needed, the three-digit rubrics were combined. Moreover, each of the 50
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rubrics of the WHO Mortality List can be obtained from the List of 282
Selected Causes of Death.
The List of 72 Selected Causes of Death was constructed by
combining titles in the List of 282 Selected Causes of Death. It is used
in tables published for the United States, for each State, and for
Metropolitan statistical areas.
The List of 61 Selected Causes of Infant Death shows more detailed
titles for Congenital anomalies and Certain conditions originating in
the perinatal period than any other list except the Each-Cause List.
The List of 34 Selected Causes of Death was created by combining
titles in the List of 72 Selected Causes. A table using this list is
published for detailed geographic areas.
Beginning with data for 1987, changes were made in these lists to
accommodate the introduction in the United States of new category
numbers *042-*044 for Human immunodeficiency virus infection. The
changes are described in the Technical Appendix from Vital Statistics
for the United States, 1987.
Effect of list revisions--The International Lists or adaptations of
them, used in the United States since 1900, have been revised
approximately every 10 years so the disease classifications may be
consistent with advances in medical science and with changes in
diagnostic practice. Each revision of the International Lists has
produced some break in comparability of cause-of-death statistics.
Cause-of-death statistics beginning with 1979 are classified by NCHS
according to the ICD-9 (15). For a discussion of each of the
classifications used with death statistics since 1900, see Vital
Statistics of the United States, 1979, Volume II, Mortality, Part A,
section 7, pages 9-14.
A dual coding study was undertaken in which the Ninth and the
Eighth Revisions were compared to measure the extent of discontinuity in
cause-of-death statistics resulting from introducing the new Revision. A
study for the List of 72 Selected Causes of Death and the List of 10
Selected Causes of Infant Death has been published (16). The List of 10
Selected Causes of Infant Death is a basic NCHS tabulation list not used
in this volume but used for provisional data in the Monthly Vital
Statistics Report, another NCHS publication. Comparability studies were
also undertaken between the Eighth and Seventh, Seventh and Sixth, and
Sixth and Fifth Revisions. For additional information about these
studies, see the 1979 Technical Appendix from Vital Statistics for the
United States, 1979.
Significant coding changes under the Ninth Revision--Since the
implementation of ICD-9 in the United States, effective with mortality
data for 1979, several coding changes have been introduced. The more
important changes are discussed as follows. In early 1983, a change that
affected data from 1981 to 1986 was made in the coding of acquired
immunodeficiency syndrome (AIDS) and HIV infection. Also effective with
data year 1981 was a coding change for poliomyelitis. For data year
1982, the definition of child was changed (which affects the
classification of deaths to a number of categories, including Child
battering and other maltreatment), and guidelines for coding deaths to
the category Child battering and other maltreatment (ICD No. E967) were
changed also. During the calendar year 1985, detailed instructions for
coding motor vehicle accidents involving all-terrain vehicles (ATV's)
clsmor91.doc - Page 11
were implemented to ensure consistency in coding these accidents.
Effective with data year 1986, "primary" and "invasive" tumors,
unspecified were classified as "malignant;" these neoplasms had been
classified to Neoplasms of unspecified nature (ICD-9 No. 239).
Beginning with data for 1987, NCHS introduced new category numbers
*042-*044 for classifying and coding HIV infection, formerly referred to
as human T-cell lymphotropic virus-III/lymphadenopathy associated virus
(HTLV-III/LAV) infection. The asterisk appearing before the category
numbers indicates these codes are not part of ICD-9. Also changed
effective with data year 1987 were coding rules for the conditions
"dehydration" and "disseminated intravascular coagulopathy." Effective
with data year 1988, minor content changes were made to the
classification for HIV infection. Detailed discussion of these changes
may be found in the technical appendix for previous volumes.
Coding in 1991--The rules and instructions used in coding the 1991
mortality medical data remained essentially the same as those used for
the 1989 and 1990 data.
Medical certification--The use of a standard classification list,
although essential for State, regional, and international comparison,
does not ensure strict comparability of the tabulated figures. A high
degree of comparability among areas could be attained only if all
records of cause of death were reported with equal accuracy and
completeness. The medical certification of cause of death can be made
only by a qualified person, usually a physician, a medical examiner, or
a coroner. Therefore, the reliability and accuracy of cause-of-death
statistics are, to a large extent, governed by the ability of the
certifier to make the proper diagnosis and by the care with which he or
she records this information on the death certificate.
A number of studies have been undertaken on the quality of medical
certification on the death certificate. In general, these have been for
relatively small samples and for limited geographic areas. A
bibliography prepared by NCHS (17), covering 128 references over 23
years, indicates no definitive conclusions have been reached about the
quality of medical certification on the death certificate. No country
has a well-defined program for systematically assessing the quality of
medical certifications reported on death certificates or for measuring
the error effects on the levels and trends of cause-of-death statistics.
One index of the quality of reporting causes of death is the
proportion of death certificates coded to the Ninth Revision Chapter
XVI, Symptoms, signs, and ill-defined conditions (ICD-9 Nos. 780-799).
Although deaths occur for which it is impossible to determine the
underlying cause, this proportion indicates the care and consideration
given to the certification by the medical certifier. This proportion
also may be used as a rough measure of the specificity of the medical
diagnoses made by the certifier in various areas. In 1991, as well as in
1990, 1.1 percent of all reported deaths in the United States, a record low,
were assigned to this category. However, trends in the percent of deaths
assigned to this category vary by age. Although the percent of deaths in
this category for all ages combined has generally remained stable since 1980,
decreases have occurred for the age group 55-64 years since 1983; and for
10-year age groups from 15 to 44 years since 1988. Between 1990 and 1991,
the percent decreased for all age groups, except for those 15-44 years and
years and 55-64 years.
clsmor91.doc - Page 12
Automated selection of underlying cause of death--Before data year
1968, mortality medical data were based on manual coding of an
underlying cause of death for each certificate in accordance with WHO
rules. Effective with data year 1968, NCHS converted to computerized
coding of the underlying cause and manual coding of all causes (multiple
causes) on the death certificate. This system is called "Automated
Classification of Medical Entities" (ACME)(18).
Beginning with data year 1990, another computer system was
implemented. This system, called "Mortality Medical Indexing,
Classification, and Retrieval" (MICAR) (19,20), automates the
coding of the multiple causes of death. The MICAR system is a major and
logical step forward in the evolution of processing mortality data.
MICAR takes advantage of the increasing capabilities of electronic data
processing to produce information that is more consistently handled than
manually processed information. In addition, MICAR ultimately will
provide more detailed information on the conditions reported on the
death certificates than is available in the ICD classification (21). In
the first year of implementation, only 5 percent (94,372) of the
Nation's death records were multiple cause coded using MICAR with
subsequent processing through ACME. For 1991 approximately 26 percent
(573,416) of the Nation's deaths were coded using MICAR. (See "Death and
fetal-death statistics" and "Medical items on the death certificate.")
The ACME system applies the same rules for selecting the underlying
cause as would be applied manually by a nosologist; however, under this
system, the computer consistently applies the same criteria, thus
eliminating intercoder variation in this step of the process.
The ACME computer program requires the coding of all conditions
shown on the medical certification. These codes are matched
automatically against decision tables that consistently select the
underlying cause of death for each record according to the international
rules. The decision tables provide the comprehensive relationships among
the conditions classified by ICD when applying the rules of selection
and modification.
The decision tables were developed by NCHS staff on
the basis of their experience in coding underlying causes of death
under the earlier manual coding system and as a result of periodic
independent validations. These tables periodically are updated to
reflect additional new information on the relationship among
medical conditions. For data year 1988, these tables were amended
to incorporate minor changes to the previously mentioned
classification for HIV infection (*042-*044) that originally had
been implemented with data year 1987. Coding procedures for
selecting the underlying cause of death by using the ACME computer
program, as well as by using the ACME decision tables, are
documented in NCHS instruction manuals (18,22,23).
Cause-of-death ranking--Cause-of-death ranking (except for infants)
is based on numbers of deaths assigned to categories in the List of 72
Selected Causes of Death and the category Human immunodeficiency virus
infection (*042-*044); cause-of-death ranking for infants is based on
the List of 61 Selected Causes of Infant Death and HIV infection. HIV
infection was added to the list of rankable causes effective with data
year 1987.
The group titles Major cardiovascular diseases and Symptoms, signs,
clsmor91.doc - Page 13
and ill-defined conditions from the List of 72 Selected Causes of Death
are not ranked; Certain conditions originating in the perinatal period
and Symptoms, signs, and ill-defined conditions from the List of 61
Selected Causes of Infant Death are not ranked. In addition, category
titles beginning with the words "Other" or "All other" are not ranked to
determine the leading causes of death. When one of the titles
representing a subtotal is ranked (such as Tuberculosis), its component
parts (in this case, Tuberculosis of respiratory system and Other
tuberculosis) are not ranked.
Maternal deaths
Maternal deaths are those for which the certifying physician has
designated a maternal condition as the underlying cause of death.
Maternal conditions are those assigned to Complications of pregnancy,
childbirth, and the puerperium (ICD-9 Nos. 630-676). In the Ninth
Revision, WHO for the first time defined a maternal death as follows:
A maternal death is defined as the death of a woman while pregnant
or within 42 days of termination of pregnancy, irrespective of
the duration and the site of the pregnancy, from any cause related
to or aggravated by the pregnancy or its management but not from
accidental or incidental causes.
Under the Eighth Revision, maternal deaths were assigned to the
category "Complications of pregnancy, childbirth, and the puerperium"
(ICDA-8 Nos. 630-678). Although WHO did not define maternal mortality,
an NCHS classification rule that limited the definition of a maternal
death to a death that occurred within a year after termination of
pregnancy from any "maternal cause," that is, any cause within the range
of ICDA-8 Nos. 630-678. This rule applied only if a duration was given
for the condition. If no duration was specified and the underlying cause
of death was a maternal condition, the duration was assumed to be within
a year and the death was coded by NCHS as a maternal death. The change
from an under-1-year limitation for duration used in the Eighth
Revision to an under-42-days limitation used in the Ninth Revision did
not have much effect on the comparability of maternal mortality
statistics. However, comparability was affected by the following
classification change. Under the Ninth Revision, maternal causes of
death have been expanded to include Indirect obstetric causes (ICD-9
Nos. 647-648). These causes include Infective and parasitic conditions
as well as other conditions present in the mother classifiable elsewhere
but that complicate pregnancy, childbirth, and the puerperium, such as
Syphilis, Tuberculosis, Diabetes mellitus, Drug dependence, and
Congenital cardiovascular disorders.
Maternal mortality rates are computed on the basis of the number of
live births. The maternal mortality rate indicates the likelihood of a
pregnant woman dying of maternal causes. The number of live births used
in the denominator is an approximation of the population of pregnant
women who are at risk of a maternal death.
Race--Beginning with the 1989 data year, NCHS changed the method of
tabulating live birth and fetal death data by race from race of child to
race of mother. This resulted in a discontinuity in maternal mortality
clsmor91.doc - Page 14
rates by race between 1989-1991 and previous years; see section on
"Change in tabulation of race data for live births and fetal deaths"
under "Infant deaths" in the Technical Appendix from Vital Statistics of the
United States, 1990.
Infant deaths
Age--Infant death is defined as a death under 1 year of age. The
term excludes fetal deaths. Infant deaths are usually divided into two
categories according to age, neonatal and postneonatal. Neonatal deaths
are those that occur during the first 27 days of life; postneonatal
deaths are those that occur between 28 days and 1 year of age.
Generally, it has been believed that different factors influencing the
child's survival predominate in these two periods: Factors associated
with prenatal development, heredity, and the birth process were
considered dominant in the neonatal period; environmental factors, such
as nutrition, hygiene, and accidents, were considered more important in
the postneonatal period. Recently, however, the distinction between
these two periods has blurred due in part to advances in neonatology,
which have enabled more very small premature infants to survive the
neonatal period.
Rates--Infant mortality rates shown in sections 2 and 8 are the
most commonly used indices for measuring the risk of dying during the
first year of life; they are calculated by dividing the number of infant
deaths in a calendar year by the number of live births registered for
the same period and are presented as rates per 1,000 or per 100,000 live
births. Infant mortality rates use the number of live births in the
denominator to approximate the population at risk of dying before the
first birthday. This measure is an approximation because some live
births will not have been exposed to a full year's risk of dying and
some of the infants who die during a year will have been born in the
previous year. The error introduced in the infant mortality rate by this
inexactness is usually small, especially when the birth rate is
relatively constant from year to year (24,25). Other sources of error
in the infant mortality rate have been attributed to differences in
applying the definitions for infant death and fetal death when
registering the event (26,27).
In contrast to infant mortality rates based on live births,
infant death rates shown in Section 1 are based on the estimated
population under 1 year of age. Infant death rates, which appear in
tabulations of age-specific death rates, are calculated by dividing the
number of infant deaths in a calendar year by the estimated midyear
population of persons under 1 year of age and are presented as rates per
100,000 population in this age group. Patterns and trends in the infant
death rate may differ somewhat from those of the more commonly used
"infant mortality rate," mainly because of differences in the nature of
the denominator and in the time reference. Whereas the population
denominator for the infant death rate is estimated using data on births,
infant deaths, and migration for the 12-month period of July-June, the
denominator for the infant mortality rate is a count of births occurring
during the 12 months of January-December. The difference in the time
reference can result in different trends between the two indices during
periods when birth rates are moving up or down markedly.
clsmor91.doc - Page 15
The infant death rate also is subject to greater imprecision than
is the infant mortality rate because of problems of enumerating and
estimating the population under 1 year of age (27).
Change in tabulation of race data for live births and fetal
deaths--Beginning with the 1989 data year, NCHS changed the method of
tabulating live birth and fetal-death data by race from race of child to
race of mother. As in previous years, race for infant and maternal deaths
(the numerator of the rate) is tabulated by the race of the decedent.
Because live births comprise the denominator of infant and maternal mortality
rates, this change resulted in a discontinuity in rates for 1989-91
data and in rates for previous years. For fetal and perinatal mortality
rates, the numerator and the denominator of the rates are affected,
resulting in a slightly smaller discontinuity. For additional information,
see the Technical Appendix from Vital Statistics of the United States, 1990.
Comparison of race data from birth and death certificates--Regardless
of whether vital events are tabulated by race of mother or by race of
child, inconsistencies exist in reporting race for the same infant
between birth and death certificates, based on results of studies in
which race on the birth and death certificates for the same infant
were compared (28).
These reporting inconsistencies can result in systematic biases in
infant mortality rates by specified race, in particular, underestimates
for specified races other than white or black. In the computation of
race-specific infant mortality rates published in Vital Statistics of
the United States, the race item for the numerator comes from the death
certificate, and for the denominator, from the birth certificate.
Biases in the rates may arise because of possible inconsistencies in
reporting race on these two vital records. Race of the mother and
father is reported on the birth certificate by the mother at the time of
delivery; whereas race of the deceased infant is reported on the death
certificate by the funeral director based on observation or on
information supplied by an informant, such as a parent. Previous studies
have noted that the race of an infant who died and was of a smaller
minority race group is sometimes reported as white on the death
certificate, but is reported as the minority race group on the birth
certificate, resulting, in the aggregate, in understatement of infant
mortality for smaller race groups (28).
Estimates can be made of the degree of bias in race-specific
infant mortality rates by comparing rates for birth cohorts based on the
newly available linked birth and infant death data set (29,30) with
period rates based on mortality data published in Vital Statistics of
the United States for the same year(s).
The comparison of cohort and period rates is somewhat affected by
small differences in the events included in the numerators of the two
rates. The numerator of the cohort rate is comprised of infant deaths
to the cohort of infants born in a calendar year whereas the numerator
of the period rate is comprised of infant deaths that occur in the
calendar year.
Based on data comparing infant mortality rates from the linked data
set for the birth cohorts of 1985-87 with period rates constructed for
1985-87, bias in the rates for the two major race groups--white and
black--is small (Table B). However, cohort rates for the smaller race
groups are estimated to be higher than period rates by 9 to 41 percent.
clsmor91.doc - Page 16
Cohort rates have not been adjusted to reflect the approximately 2
percent of infant death records that were not linked to their
corresponding birth records. Because of systematic understatement of
infant mortality rates based on period data, data from the national
linked files should be used to measure infant mortality for races other
than black and white. For the major race groups, period data are a
close approximation of the rates based on linked files.
Table B. Infant mortality rates by race of mother for the period 1985-87
and for birth cohorts, 1985-87; and ratio of birth cohort to period rates:
United States
[Rates per 1,000 live births in specified groups]
_____________________________________________________________________________
Period Birth Ratio
rate cohort rate cohort/
Race 1985-87 1985-87 period rates
_____________________________________________________________________________
All races 10.4 10.1 0.97
White 8.8 8.5 0.97
Black 18.9 18.2 0.96
American Indian 12.2 13.3 1.09
Chinese 5.5 6.0 1.09
Japanese 5.3 6.6 1.25
Filipino 5.1 7.2 1.41
Other Asian or
Pacific Islander 7.0 8.3 1.19
_____________________________________________________________________________
NOTE: Births for race not stated are not distributed.
Hispanic origin--Infant mortality rates for the Hispanic-origin
population are based on numbers of resident infant deaths reported to be
of Hispanic origin and numbers of resident live births by Hispanic
origin of mother for the 47 States, New York State (excluding New York
City), and the District of Columbia. In computing infant mortality
rates, deaths and live births of unknown origin are not distributed
among the specified Hispanic and non-Hispanic groups. Because the
percent of infant deaths of unknown origin for 1991 was 1.6 percent and
the percent of live births of unknown origin was 0.8 percent, infant
mortality rates by specified Hispanic origin and race for non-Hispanic
origin are slightly underestimated.
Caution should be exercised when comparing infant mortality rates
among the Hispanic population (especially Puerto Ricans) and
non-Hispanic population for 1991. Because the percent unknown origin for
all ages for New York City was about 21 percent on a place-of-occurrence
basis, infant mortality data for New York City was excluded from tables
2-22--2-25. The percent unknown origin on place-of-residence basis for
infant deaths for New York City for 1991 was about 30 percent (about 5
percent for live births). Also, because New York City accounted for
about 31 percent of the live births to Puerto Ricans in the United
States in 1991, excluding the data for New York City may have an impact
on infant mortality rates for the Hispanic population, especially for
Puerto Ricans. The effect of including and excluding infant deaths and
live births for New York City on the infant mortality rates for the total
clsmor91.doc - Page 17
area for 1990 are shown in table C of the Technical Appendix from Vital
Statistics of the United States, 1990. The effect for 1991 would be similar.
In addition, as discussed above for specified races, period infant
mortality rates for specific Hispanic-origin groups tend to be under-
estimated when compared with rates based on the national linked birth and
infant death data set as shown in Table C. Comparisions also are affected
by the approximate 2 percent of infant death records that are not linked to
the corresponding birth records.
Caution should be exercised when generalizing from the ratios of cohort-
to-period rates for 1986-87 with data for 1991, because the area for Hispanic
data has expanded from 18 States and the District of Columbia in 1986-87 to
47 States, New York(excluding New York City), and the District of Columbia
in 1991. The Hispanic area for 1986-87 included Arizona, Arkansas,
California, Colorado, District of Columbia, Georgia, Hawaii, Illinois,
Indiana, Kansas, Mississippi, Nebraska, New Jersey, New York, North Dakota,
Ohio, Texas, Utah, and Wyoming.
Small numbers of infant deaths for specific Hispanic-origin groups can
result in infant mortality rates subject to relatively large random variation
(see "Random variation in numbers of deaths, death rates, and mortality rates
and ratios").
Tabulation list--Causes of death for infants are tabulated according to
a list of causes that is different from the list of causes for the
population of all ages, except for the Each Cause List. (See "Cause-of-death
classification" under "Cause of death.")
Table C. Infant mortality rates by specified Hispanic origin of mother and
race of mother for mothers of non-Hispanic origin for the period 1986-87 and
birth cohorts 1986 and 1987 combined; and ratio of birth cohort to period
rates: Total of 18 reporting States and the District of Columbia
[Rates per 1,000 live births in specified group. Figures for origin not
stated included in "All origins" but not distributed among origin groups]
____________________________________________________________________________
Birth
Origin Period rate cohort rate Ratio cohort/
1986-87 1986-87 period rates
____________________________________________________________________________
All origins 10.1 9.7 0.96
Hispanic total 8.0 8.3 1.04
Mexican 7.6 7.9 1.04
Puerto Rican 7.9 10.9 1.37
Cuban 6.5 7.9 1.22
Other Hispanic1 9.1 8.3 0.91
Non-Hispanic total2 9.9 9.9 1.00
Non-Hispanic White 8.3 8.2 0.99
Non-Hispanic Black 17.5 17.7 1.01
_____________________________________________________________________________
1Includes Central and South American, and other and unknown Hispanic.
2Includes races other than white and black.
clsmor91.doc - Page 18
Fetal deaths
In May 1950, WHO recommended the following definition of fetal
death be adopted for international use:
Death prior to the complete expulsion or extraction from its
mother of a product of conception, irrespective of the duration of
pregnancy; the death is indicated by the fact that after such
separation, the fetus does not breathe or show any other evidence
of life such as beating of the heart, pulsation of the umbilical
cord, or definite movement of voluntary muscles (31).
The term "fetal death" was defined on an all-inclusive basis to
end confusion arising from the use of such terms as stillbirth,
spontaneous abortion, and miscarriage.
Shortly thereafter, this definition was adopted by NCHS as the
nationally recommended standard. All registration areas except Puerto
Rico have definitions similar to the standard definition (32). Puerto
Rico has no formal definition.
As another step toward increasing the comparability of data on
fetal deaths for different countries, WHO recommended that for
statistical purposes fetal deaths be classified as early, intermediate,
and late. These groups are defined as follows:
Less than 20 completed weeks of gestation
(early fetal deaths)...................... Group I
20 completed weeks of gestation but less than
28 (intermediate fetal deaths).............. Group II
28 completed weeks of gestation and over
(late fetal deaths)........................ Group III
Gestation period not classifiable in groups I, II,
and III.......................................Group IV
As shown in table 3-11, Group IV consists of fetal deaths with
gestation not stated but presumed to be 20 weeks or more.
Until 1939, the nationally recommended procedure for registration
of a fetal death required the filing of a live-birth certificate and a
death certificate. In 1939, a separate Standard Certificate of
Stillbirth (fetal death) was created to replace the former procedure.
This was revised in 1949, 1956, 1968, 1978, and 1989. The 1989 U.S.
Standard Report of Fetal Death is shown in figure 7-B.
The 1977 revision of the Model State Vital Statistics Act and Model
State Vital Statistics Regulations (33) recommended spontaneous fetal
deaths at a gestation of 20 weeks or more or a weight of 350 grams or
more and all induced terminations of pregnancy regardless of gestational
age be reported and further be reported on separate forms. These forms
should be considered legally required statistical reports rather than
legal documents.
Beginning with fetal deaths reported in 1970, procedures were
implemented that attempted to separate reports of spontaneous fetal
deaths from those of induced terminations of pregnancy. These procedures
were implemented because the health implications of spontaneous fetal
clsmor91.doc - Page 19
deaths are different from those of induced terminations of pregnancy.
These procedures are still used.
Comparability and completeness of data--Registration area
requirements for reporting fetal deaths vary. Most of the areas require
reporting of fetal death at gestations of 20 weeks or more. Table D
shows the minimum period of gestation required by each State to report
fetal death in 1991. Substantial evidence exists that indicates some fetal
deaths for which reporting is required are not reported (34,35).
Table D. Period of gestation at which fetal-death reporting is required: Each
reporting area, 1991
______________________________________________________________________________
|All | | |20 |20 |20 | | |
|periods| | |wks |wks. |wks. | | |
|of | 16 | 20 |or |or |or |5 | 350 | 500
|gesta- | wks | wks |350 |400 |500 |mos.|grams|grams
Area |tion | | |grams |grams |grams | | |
____________________|_______|_____|_____|______|______|______|____|_____|_____
Alabama | X
Alaska | X
Arizona | 1X
Arkansas | 2X
California | X
Colorado | 2X
Connecticut | X
Delaware | X
District of Columbia| X
Florida | X
Georgia | X
Hawaii | X
Idaho | X
Illinois | X
Indiana | X
Iowa | X
Kansas | X
Kentucky | X
Louisiana | X
Maine | 2X
Maryland | 3X
Massachusetts | X
Michigan | X
Minnesota | X
Mississippi | X
Missouri | X
Montana | X
Nebraska | X
Nevada | X
New Hampshire | X
New Jersey | X
New Mexico | X
clsmor91.doc - Page 20
New York |
New York excluding|
New York City | X
New York City | X
North Carolina | X
North Dakota | X
Ohio | X
Oklahoma | X
Oregon | 4X
Pennsylvania | X
Rhode Island | X
South Carolina | X
South Dakota | X
Tennessee | 5X
Texas | X
Utah | X
Vermont | 6X
Virginia | X
Washington | X
West Virginia | X
Wisconsin | X
Wyoming | X
Puerto Rico |
Virgin Islands | X X
Guam | X
_____________________________________________________________________________
1.If gestational age is unknown, weight of 350 grams or more.
2.Although State law requires the reporting of fetal deaths of all
periods of gestation, only data for fetal deaths of 20 weeks
of gestation or more are provided to NCHS.
3.If gestational age is unknown, weight of 500 grams or more.
4.If gestational age is unknown, weight of 400 grams or more, or
crown-heel length of 28 centimeters or more.
5.If weight is unknown, 22 completed weeks of gestation or more.
6.If gestational age is unknown, weight of 400 more grams, 15 ounces or
more.
Underreporting of fetal deaths is most likely to occur in the
earlier part of the required reporting period for each State(34). Thus for
States requiring reporting of all periods of gestation, fetal deaths
occurring under 20 weeks of gestation are less completely reported; for
States requiring reporting of fetal deaths of 20 weeks of gestation or more,
fetal deaths occurring at 20-23 weeks of gestation are less completely
reported. Thus, reporting of fetal deaths at 20-23 weeks of gestation may
be more complete for those States that report fetal deaths at all periods
of gestation than for others.
To maximize the comparability of data by year and by State, most of
the tables in section 3 are based on fetal deaths occurring at
gestations of 20 weeks or more. These tables also include fetal deaths
for which gestation is not stated for those States requiring reporting
at 20 weeks or more gestation only. Beginning with 1969, fetal deaths of
not stated gestation were excluded for States requiring reporting of all
products of conception except for those with a stated birthweight of 500
clsmor91.doc - Page 21
grams or more. In 1991, this rule was applied to the following States:
Georgia, Hawaii, New York (including New York City), Rhode Island, and
Virginia. Each year, there are exceptions to this procedure.
Arkansas--Since 1971, Arkansas has been using two reporting forms
for fetal deaths: A confidential Spontaneous Abortion form that is not
sent to NCHS and a Fetal Death Certificate that is. Because of State changes
concerning fetal-death registration in 1981 and 1984(see Technical Appendix
from Vital Statistics of the United States, 1990), the comparability of counts
of early fetal deaths may be affected. In particular, counts of fetal deaths
at 20 to 27 weeks for 1981-83 were not comparable between Arkansas and other
reporting areas or with Arkansas data for 1984-91. It is believed that
reporting has improved but is still not comparable with data for 1980 and
earlier years.
Colorado--Although Colorado State law requires reporting fetal deaths
of all periods of gestation, beginning in 1989 the State provides to
NCHS only data for fetal deaths of 20 weeks gestation or more.
Maine--Maine uses two reporting forms for fetal deaths: A Report
of Abortion (Spontaneous and Induced) and a Report of Fetal Death. Most
spontaneous fetal deaths at less than 20 weeks' gestation are reported
on the Report of Abortion, and, therefore, are excluded from fetal death
counts in this volume.
Maryland--From the counts of frequencies by month, it appears that
not all fetal deaths occurring in the first quarter of 1989 were
reported. This may account in part for the lower fetal mortality rates
for Maryland for 1989 relative to contiguous years shown in table 3-5.
New York City--As a result of local efforts to improve reporting,
a combined total of 10,470 additional 1990 and 1991 fetal-death records were
sent from New York City hospitals after the data files had been processed and
tabulated. Most of these records are for fetal deaths under 20 weeks of
gestation or not-stated gestation. The values in the tables, particularly
table 3-1, that show fetal deaths for all periods of gestation exclude the
additional deaths.
Revised Report of Fetal Death for 1989--Beginning with data for
1989, new items were added to the U.S. Standard Report of Fetal Death,
including Hispanic origin of the mother and father, medical and other
risk factors of pregnancy, obstetric procedures, and method of delivery.
In addition, questions on complications of labor and/or delivery and
congenital anomalies of fetus were changed from an open-ended question
to a checkbox format to ensure more complete reporting of information.
The tabulation of items in the fetal-death section is limited to
those States whose reporting is sufficiently complete. For fetal deaths
before data year 1991, data were published when a State had a response
for the item on at least 20 percent of the records. Beginning in data
year 1991, tabulations of prenatal care and educational attainment include
only those States with a response for that specific item on at least 80
percent of the fetal-death records. For the other tables in the fetal-death
section, item completion is high and no reporting criterion is used to
exclude States.
Period of gestation--The period of gestation is the number of
completed weeks elapsed between the first day of the last normal
clsmor91.doc - Page 22
menstrual period (LMP) and the date of delivery. The first day of the
LMP is used as the initial date because it can be more accurately
determined than the date of conception, which usually occurs 2 weeks
after LMP. Data on period of gestation are computed from information on
"date of delivery" and "date last normal menses began." If "date last
normal menses began" is not on the record or if the calculated gestation
falls beyond a duration considered biologically plausible, the
"Physician's estimate of gestation" is used.
To improve data quality, beginning with data for 1989, NCHS
instituted a new computer edit to check for consistency between
gestation and birthweight (36). Briefly, if LMP gestation is
inconsistent with birthweight, and the physician's estimate is
consistent, the physician's estimate is used; if both are inconsistent,
LMP gestation is used, and birthweight is assigned to unknown. When the
period of gestation is reported in months on the report, it is allocated
to gestational intervals in weeks as follows:
1 - 3 months to under 16 weeks
4 months to 16 - 19 weeks
5 months to 20 - 23 weeks
6 months to 24 - 27 weeks
7 months to 28 - 31 weeks
8 months to 32 - 35 weeks
9 months to 40 weeks
10 months and over to 43 weeks and over
All areas except Puerto Rico reported LMP in 1991, and all areas except
California, Louisiana, Maryland, and Oklahoma reported physician's estimate
of gestation.
Birthweight--Most of the 55 registration areas do not specify how
weight should be given, that is, in pounds and ounces or in grams. In
the tabulation and presentation of birthweight data, the metric system
(grams) has been used to facilitate comparison with other data published
in the United States and internationally. Birthweight specified in
pounds and ounces is assigned the equivalent of the gram intervals, as
follows:
Less than 500 grams = 0 lb 1 oz or less
500 - 999 grams = 1 lb 2 oz - 2 lb 3 oz
1,000 - 1,499 grams = 2 lb 4 oz - 3 lb 4 oz
1,500 - 1,999 grams = 3 lb 5 oz - 4 lb 6 oz
2,000 - 2,499 grams = 4 lb 7 oz - 5 lb 8 oz
2,500 - 2,999 grams = 5 lb 9 oz - 6 lb 9 oz
3,000 - 3,499 grams = 6 lb 10 oz - 7 lb 11 oz
3,500 - 3,999 grams = 7 lb 12 oz - 8 lb 13 oz
4,000 - 4,499 grams = 8 lb 14 oz - 9 lb 14 oz
4,500 - 4,999 grams = 9 lb 15 oz - 11 lb 0 oz
5,000 grams or more = 11 lb 1 oz or more
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With the introduction of ICD-9, the birthweight classification
intervals for perinatal mortality statistics were shifted downward by 1
gram as shown above. Previously, the intervals were, for example,
1,001-1,500, 1,501-2,000, and so forth. Beginning in 1989, NCHS
instituted a consistency check between birthweight and gestation; see
previous section on gestation.
Race--Beginning with data for 1989, NCHS changed the method of
tabulating fetal death, perinatal, and live birth data by race from race
of child to race of mother. When the race of the mother is unknown, the
mother is assigned the father's race; when information for both parents
is missing, the race of the mother is assigned to the specific race of the
mother of the preceding record with known race.
The change in tabulation of race has resulted in a discontinuity in
fetal mortality rates by race for data years 1989-91 relative to previous
years; see "Change in tabulation of race data for live births and fetal
deaths" under "Infant deaths."
Hispanic origin of mother--Fetal mortality data for the
Hispanic-origin population are based on fetal deaths to mothers of
Hispanic origin who were residents of those States and the District of
Columbia that included items on the report of fetal death to identify
Hispanic or ethnic origin of mother. Data for 1991 were obtained from
45 States and the District of Columbia; areas not supplying data were
Louisiana, Maryland, Massachusetts, New Hampshire, and Oklahoma.
For 1991, fetal and perinatal mortality data in table 3-18 and 4-6 are
for 45 States and the District of Columbia and tables 3-19 and 4-7 are
for 36 States and the District of Columbia that had an item on Hispanic
or ethnic origin on the death certificate, birth certificate, and report
of fetal death and whose data for all three files were at least 90
percent complete on a place-of-occurrence basis and considered to be
sufficiently comparable to be used for analysis. The States included
are Alabama, Alaska, Arizona, Arkansas, California, Colorado, Delaware,
Florida, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Minnesota,
Mississippi, Missouri, Nebraska, Nevada, New Jersey, New Mexico, North
Carolina, North Dakota, Ohio, Oregon, Pennsylvania, South Carolina, South
Dakota, Tennessee, Texas, Utah, Vermont, Virginia, West Virginia, Wisconsin,
and Wyoming.
The 36 States and the District of Columbia for which fetal and
perinatal data by Hispanic origin are shown accounted for about 83
percent of the Hispanic population in 1990, including 96 percent of the
Mexican population, 45 percent of the Puerto Rican population, 88
percent of the Cuban population, and 71 percent of the "Other Hispanic"
population (13). Accordingly, caution should be exercised in
generalizing mortality patterns from the reporting area to the
Hispanic-origin population (especially Puerto Ricans) of the entire
United States. (See also "Hispanic origin" under "Classification of
data").
Total-birth order--Total-birth order refers to the sum of live
births and other terminations (including spontaneous fetal deaths and
induced terminations of pregnancy) a woman has had, including the fetal
death being recorded. For example, if a woman has given birth to two
live babies and to one born dead, the next fetal death to occur is
counted as number four in total-birth order.
Beginning with implementation of the 1989 revision of the U. S.
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Standard Report of Fetal Death, total-birth order is calculated from
three items on pregnancy history: number of previous live births now
living; number of previous live births now dead; and number of other
terminations (spontaneous and induced at anytime after conception). For
prior years, total-birth order was calculated from four items, see the
Technical Appendix from Vital Statistics of the United States 1988.
Although all registration areas use the two standard items
pertaining to number of previous live births, registration areas phrase
the item pertaining to other terminations of pregnancy differently.
Total-birth order for all areas is calculated from the sum of available
information. Thus, information on total-birth order may not be
completely comparable among the registration areas. In addition, there
may be substantial underreporting of other terminations of pregnancy on
the fetal death report.
Marital status--Table 3-3 shows fetal deaths and fetal-death rates
by mother's marital status. The following states were excluded from
this table because their reports of fetal death did not include an item
on marital status: California, Connecticut, Maryland, Michigan, Nevada,
New York (including New York City), and Texas. Because live births
comprise the denominator of the rate, marital status must be reported
for mothers of live births. Marital status of the mother of the live
birth is inferred for States that did not report it on the birth
certificate.
Beginning with data for 1989, fetal death reports with marital
status not stated are shown as not stated in frequencies, but are
proportionally distributed for rate computations into either the married
or unmarried categories according to the percent of fetal death reports
with stated marital status that fall into each category for the
reporting States. Before 1989, fetal death reports with not-stated
marital status were assigned to the married category. Because of this
change, fetal death frequencies and rates by marital status for 1989 through
1991 are not strictly comparable with those for previous years.
No quantitative data exist on the characteristics of unmarried
women who do not report, misreport their marital status, or fail to
register fetal deaths. Underreporting may be greater for the unmarried
group than for the married group.
Age of mother--Beginning with data for 1989, the U.S. Standard
Report of Fetal Death asks for the mother's date of birth. Age of mother
is computed from the mother's date of birth and the date of the
termination of the pregnancy. For those States whose certificates do
not contain an item for the mother's date of birth, reported age of the
mother (in years) is used. The age of the mother is edited in NCHS for
upper and lower limits. When mothers are reported to be under 10 years
of age or 50 years of age and over, the age of the mother is considered
not stated and is assigned as follows: Age on all fetal-death records
with age of mother not stated is assigned according to the age appearing
on the record previously processed for a mother of identical race and
having the same total-birth order (total of live births and other
terminations).
Sex of fetus--Beginning with data for 1989, for all fetal deaths of
20 or more weeks gestation, not-stated sex of fetus is assigned the sex
of the fetus from the previous record. Before 1989, no such assignment
was made.
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Plurality--All registration areas except Louisiana report the
plurality of the fetus. Although Louisiana has not reported this item
for many years, prior to 1989, data for Louisiana was erroneously
converted to a plurality of 1 (single birth) and included in United
States totals. Beginning with 1989 data, Louisiana is excluded from tables
reporting plurality of the fetus. For reporting areas, not-stated
plurality of the fetus is assigned to single births.
Perinatal mortality
Perinatal definitions--Beginning with data year 1979, perinatal
mortality data for the United States and each State have been published
in section 4. WHO recommends in ICD-9, "national perinatal statistics
should include all fetuses and infants delivered weighing at least 500
grams (or when birthweight is unavailable, the corresponding gestational
age (22 weeks) or body length (25 cm crown-heel)), whether alive or
dead...." It further recommends, "countries should present, solely for
international comparisons, 'standard perinatal statistics' in which both
the numerator and denominator of all rates are restricted to fetuses and
infants weighing 1,000 grams or more (or, where birthweight is
unavailable, the corresponding gestational age (28 weeks) or body length
(35 cm crown-heel))." Because birthweight and gestational age are not
reported on the death certificate in the United States, NCHS was unable
to adopt these definitions. Three definitions of perinatal mortality
are used by NCHS: Perinatal Definition I, generally used for
international comparisons, which includes fetal deaths of 28 weeks'
gestation or more and infant deaths of less than 7 days; Perinatal
Definition II, which includes fetal deaths of 20 weeks' gestation or
more and infant deaths of less than 28 days; and Perinatal Definition
III, which includes fetal deaths of 20 weeks' gestation or more and
infant deaths of less than 7 days.
Variations in fetal death reporting requirements and practices have
implications for comparing perinatal rates among States. Because
reporting is generally sporadic near the lower limit of the reporting
requirement, States that require reporting of all products of pregnancy,
regardless of gestation, are likely to have more complete reporting of
fetal deaths at 20 weeks or more than those States that do not. The
larger number of fetal deaths reported for these "all periods" States
may result in higher perinatal mortality rates than those rates reported
for States whose reporting is less complete. Accordingly, reporting
completeness may account, in part, for differences among the State
perinatal rates, particularly differences for Definitions II and III,
which use data for fetal deaths at 20-27 weeks.
Not stated--Fetal deaths with gestational age not stated are
presumed to be of 20 weeks' gestation or more if the State requires
reporting of all fetal deaths at a gestational age of 20 weeks or more
or the fetus weighed 500 grams or more in those States requiring
reporting of all fetal deaths, regardless of gestational age. For
Definition I, fetal deaths at a gestation not stated but presumed to
have been of 20 weeks or more are allocated to the category 28 weeks or
more, according to the proportion of fetal deaths with stated
clsmor91.doc - Page 26
gestational age that falls into that category. For Definitions II and
III, fetal deaths at a presumed gestation of 20 weeks or more are
included with those at a stated gestation of 20 weeks or more.
The allocation of not-stated gestational age for fetal deaths is
made individually for each State, for metropolitan and nonmetropolitan
areas, and separately for the entire United States. Accordingly, the sum
of perinatal deaths for the areas according to Definition I may not
equal the total number of perinatal deaths for the United States.
Race--Beginning with the 1989 data year, NCHS has changed the method
of tabulating fetal death and live birth data by race from race of child
to race of mother. This has resulted in a discontinuity in perinatal
mortality rates by race between 1989 and previous years; see "Change in
race classification for live births and fetal deaths" under "Infant
deaths."
Hispanic origin--See "Hispanic origin of mother" under "Fetal
deaths."
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